1 files changed, 94 insertions, 0 deletions
diff --git a/src/lib/net.c b/src/lib/net.c
new file mode 100644
index 0000000..7c899d7
--- /dev/null
+++ b/src/lib/net.c
@@ -0,0 +1,94 @@
+/*
+ *   This program is is free software; you can redistribute it and/or modify
+ *   it under the terms of the GNU General Public License, version 2 of the
+ *   License as published by the Free Software Foundation.
+ *
+ *   This program is distributed in the hope that it will be useful,
+ *   but WITHOUT ANY WARRANTY; without even the implied warranty of
+ *   MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ *   GNU General Public License for more details.
+ *
+ *   You should have received a copy of the GNU General Public License
+ *   along with this program; if not, write to the Free Software
+ *   Foundation, Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301, USA
+ */
+
+/**
+ * $Id$
+ * @file net.c
+ * @brief Functions to parse raw packets.
+ *
+ * @author Arran Cudbard-Bell <a.cudbardb@freeradius.org>
+ * @copyright 2014-2015 Arran Cudbard-Bell <a.cudbardb@freeradius.org>
+ */
+ #include <freeradius-devel/libradius.h>
+ #include <freeradius-devel/net.h>
+
+/** Calculate UDP checksum
+ *
+ * Zero out UDP checksum in UDP header before calling fr_udp_checksum to get 'expected' checksum.
+ *
+ * @param data Pointer to the start of the UDP header
+ * @param len value of udp length field in host byte order. Must be validated to make
+ *	  sure it won't overrun data buffer.
+ * @param checksum current checksum, leave as 0 to just enable validation.
+ * @param src_addr in network byte order.
+ * @param dst_addr in network byte order.
+ * @return 0 if the checksum is correct, else another number.
+ */
+uint16_t fr_udp_checksum(uint8_t const *data, uint16_t len, uint16_t checksum,
+			 struct in_addr const src_addr, struct in_addr const dst_addr)
+{
+	uint64_t sum = 0;	/* using 64bits avoids overflow check */
+	uint16_t const *p = (uint16_t const *)data;
+
+	uint16_t const *ip_src = (void const *) &src_addr.s_addr;
+	uint16_t const *ip_dst = (void const *) &dst_addr.s_addr;
+	uint16_t i;
+
+	sum += *(ip_src++);
+	sum += *ip_src;
+	sum += *(ip_dst++);
+	sum += *ip_dst;
+
+	sum += htons(IPPROTO_UDP);
+	sum += htons(len);
+
+	for (i = len; i > 1; i -= 2) {
+		sum += *p++;
+	}
+
+	if (i) {
+		sum += (0xff & *(uint8_t const *)p) << 8;
+	}
+
+	sum -= checksum;
+
+	while (sum >> 16) {
+		sum = (sum & 0xffff) + (sum >> 16);
+	}
+
+	return ((uint16_t) ~sum);
+}
+
+/** Calculate IP header checksum.
+ *
+ * Zero out IP header checksum in IP header before calling fr_iph_checksum to get 'expected' checksum.
+ *
+ * @param data Pointer to the start of the IP header
+ * @param ihl value of ip header length field (number of 32 bit words)
+ */
+uint16_t fr_iph_checksum(uint8_t const *data, uint8_t ihl)
+{
+	uint64_t sum = 0;
+	uint16_t const *p = (uint16_t const *)data;
+
+	uint8_t nwords = (ihl << 1); /* number of 16-bit words */
+
+	for (sum = 0; nwords > 0; nwords--) {
+		sum += *p++;
+	}
+	sum = (sum >> 16) + (sum & 0xffff);
+	sum += (sum >> 16);
+	return ((uint16_t) ~sum);
+}